At 10:16 AM 10/22/98 , Bill Frantz wrote:
>I think there are at least 3 kinds of languages in the world. They are:
>(1) Write only: HP calculator language for example. ...
>(2) Write and revise: C, Algol and most such are examples. ...
>(3) Algorithm publication: MIX?, C with buffer overruns? ...
>Where in this spectrum does E stand.
[a] E intends to support all three styles of use, in order from highest to lowest priority: #2, #3, #1
Even though it's last, E takes #1 quite seriously. Not that we seek to enable programs to be hard to read, but that, in order to be a command language, we have to support well the short program that only gets executed once.
There are two interpretations of #2: "revise" as in rapid prototyping, and "revise" as in serious large-scale software engineering and maintenance. E should support both as well as Smalltalk & Self. But as with Smalltalk & Self, E sacrifices two needs of large-scale efforts: static type checking and close-to-the-machine implementation. The first helps catch errors early, and the second enables the programmer to better predict a program's performance (as opposed to enabling a program to perform better).
Your distinction between #2 and #3 is dead on. E code and E pseudo code properly differ in three ways
Using more words,
Such E pseudo code is a fine executable specification for real E code.
>There is one case in the E runtime where we iterate over a changing
>collection. Consider the connection building operation. The basic call
> getConnection(String vatID, String plsList);
>... If the address is a VLS, the
>address(es) it returns will be added to the set and tried next. ...
>This process would be a lot more difficult with static snapshots.
[+] Don't snapshot in this case.
The "snapshot" semantics is only meant to explain E's for-loop, and the table class's Enumeration-yielding operations -- they all iterate over a snapshot of the collection made when either the for-loop was started or the Enumeration was requested. Since the above doesn't use either for its iteration, there's no conflict.